OFDM is a method of encoding data on multiple carriers that are mutually orthogonal for enhancement in frequency utilization efficiency and robustness to frequency-selective fading channels. It is also advantageous for achieving fast modulation/demodulation at the transmission/reception node using Inverse Fast Fourier Transform (IFFT) and Fast Fourier Transform (FFT). Such features of OFDM are suitable for high-speed data transmission; thus, they are adopted as a standard transmission scheme for 3rd Generation Partnership Project (3GPP) Long-Term Evolution (LTE) and Institute of Electrical and Electronics Engineers (IEEE) 802.11 and 802.16.
In a downlink of an OFDM-based cellular communication system, a Reference Signal (RS) for use in channel estimation and a data channel carrying information destined for a terminal are mapped to a tone corresponding to a subcarrier and an OFDM symbol according to a system specific rule for transmission. A terminal, to acquire the information transmitted thereto, estimates channel response based on the RS and performs demodulation on the data channel received based on the estimated channel response.